Danionella

Danionella is a genus of danionin fish found in freshwater habitats in Myanmar and West Bengal, India. It includes some of the smallest fishes.

Danionella
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Subfamily: Danioninae
Genus: Danionella
T. R. Roberts, 1986
Type species
Danionella translucida
T. R. Roberts, 1986
Species

See text

Distribution

All species of Danionella are found in Myanmar. D. translucida is described from the Ayeyarwady River basin, and D. mirifica was described from the Kaiming area in upper Myanmar.[1]

Description

When first described, Danionella translucida was the smallest ostariophysan and the smallest adult vertebrate to inhabit fresh water.[2] Its adult size ranges from 10–12 millimetres (.43–.47 in) SL.[2] D. mirifica gets slightly larger, at about 14 mm (.55 in) SL, but is still one of the smallest freshwater fishes.[1][3]

Danionella species lack scales and barbels, [2] but possess a lateral line.[4]

D. mirifica has a single row of melanophores between the pelvic fins and the tips of the cleithra, and there is a lack of melanophores on the underside of the abdomen.[1]

D. dracula reaches 17 mm in length. It is neotonous, lacking 44 bones that develop late in the related zebrafish Danio rerio. They have teeth made of bone, rather than the true teeth of other fishes, and the males have a pair of boney fangs which the use for sparring for mates. Britz et al. believe the lineage lost true teeth about 50 Ma.[5]

Species

References
  1. Britz, Ralf (October 2003). "Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae)" (PDF). Ichthyol. Explor. Freshwaters. 14 (3): 217–222. Retrieved 2009-06-24.
  2. Roberts, Tyson R. (1986). "Danionella translucida, a new genus and species of cyprinid fish from Burma, one of the smallest living vertebrates". Environmental Biology of Fishes. 16 (4): 231–241. doi:10.1007/BF00842977.
  3. Froese, Rainer and Pauly, Daniel, eds. (2011). "Danionella mirifica" in FishBase. August 2011 version.
  4. Hu, Yinan; Mauri, Angela; Donahue, Joan; Singh, Rajendra; Acosta, Benjamin; McMenamin, Sarah (2019). "Thyroid hormone coordinates developmental trajectories but does not underlie developmental truncation in danionins". Developmental Dynamics. 248 (11): 1144–1154. doi:10.1002/dvdy.76. ISSN 1097-0177. PMC 6824966. PMID 31228301.
  5. Ralf Britz et al., Royal Society's journal Proceedings B, March 2009
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